Sheet feed roll

ABSTRACT

A sheet feed roll having a concavity and a convexity formed on an outer peripheral surface thereof, an irregular portion composed of the concavity and the convexity being of a corrugated cross-sectional shape, and the concavity extending along the axial direction of the roll.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to various sheet feed rolls for use in sheet feeding apparatuses of various types of office automation equipment, including various printers, such as ink jet printers (to be hereinafter referred to as IJP), copiers and facsimile machines (FAX), and automated teller machines (ATM).

2. Description of the Related Art

Rolls, which comprise a resin core or a metal shaft and EPDM (ethylene-propylene-diene rubber), chlorinated polyethylene rubber, silicone rubber, polyurethane rubber, etc., have so far been used as sheet feed rolls of IJP, FAX and ATM. Some of these rolls have a grain patter, a polished pattern or the like on their outer peripheral surfaces (Japanese Patent Application Laid-Open (kokai) Nos. 8-108591, 5-221059, and 10-071655).

With the above-mentioned rolls, however, the problems remain unsolved that they have inadequate sheet feed performance, they are susceptible to a load and a sheet feed speed, and their sheet feed performance is unstable. Thus, further improvements are required of them.

SUMMARY OF THE INVENTION

The present invention has been accomplished in the light of the above-mentioned circumstances. It is an object of the present invention to provide a sheet feed roll which has higher sheet feed performance and can perform stable sheet feed.

A first aspect of the present invention for attaining the above object is a sheet feed roll having a concavity and a convexity formed on an outer peripheral surface thereof, an irregular portion composed of the concavity and the convexity being of a corrugated cross-sectional shape, and the concavity extending along an axial direction of the roll.

A second aspect of the present invention is the sheet feed roll according to the first aspect, characterized in that a width of the concavity is 500 μm or less.

A third aspect of the present invention is the sheet feed-roll according to the first aspect, characterized in that a width of the convexity is 500 μm or less.

A fourth aspect of the present invention is the sheet feed roll according to the first aspect, characterized in that a width of the concavity is 500 μm or less, and a width of the convexity is 500 μm or less.

A fifth aspect of the present invention is the sheet feed roll according to any one of the first to fourth aspects, characterized in that when the outer peripheral surface of the roll is partitioned by a lattice of cells 1 mm square each, one or more of the convexities and one or more of the concavities are present in each of the cells.

A sixth aspect of the present invention is the sheet feed roll according to any one of the first to fifth aspects, characterized in that a height of the convexity is 50 to 150 μm.

A seventh aspect of the present invention is the sheet feed roll according to any one of the first to sixth aspects, comprising polyurethane having a hardness of 25 to 50° (JIS A), and rebound resilience of 50 to 80%.

An eighth aspect of the present invention is the sheet feed roll according to any one of the first to seventh aspects, having Rz of 40 to 120 μm.

A ninth aspect of the present invention is the sheet feed roll according to any one of the first to eighth aspects, characterized in that a length in the axial direction of the concavity is two times or more a length in a circumferential direction of the concavity.

A tenth aspect of the present invention is the sheet feed roll according to any one of the first to ninth aspects, characterized in that a length in the axial direction of the convexity is two times or more a length in a circumferential direction of the convexity.

An eleventh aspect of the present invention is the sheet feed roll according to any one of the first to tenth aspects, characterized in that outer peripheral corners in opposite end portions in a longitudinal direction of the sheet feed roll have C-surfaces or R-surfaces.

A twelfth aspect of the present invention is a sheet feed roll comprising polyurethane having a hardness of 25 to 50° (JIS A), and rebound resilience of 50 to 80%, and the sheet feed roll having a concavity and a convexity formed on an outer peripheral surface thereof, an irregular portion composed of the concavity and the convexity being of a corrugated cross-sectional shape, and characterized in that the concavity extends along an axial direction of the roll, a width of the concavity is 500 μm or less, a width of the convexity is 500 μm or less, a height of the convexity is 50 to 150 μm, and Rz of the sheet feed roll is 40 to 120 μm.

As described above, a sheet feed roll has a concavity and a convexity formed on an outer peripheral surface thereof, an irregular portion composed of the concavity and the convexity being of a corrugated cross-sectional shape, and the concavity extending along the axial direction of the roll. Since this sheet feed roll has high sheet feed performance and can perform stable sheet feed, it can be preferably used as a separating roll, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions in conjunction with the accompanying drawings.

FIG. 1 is a schematic perspective view representing an image of the sheet feed roll of the present invention.

FIG. 2 is a schematic view showing a state in which a plurality of concavities are provided on the outer peripheral surface of the sheet feed roll of the present invention.

FIGS. 3A and 3B are enlarged views of a cross section of the sheet feed roll of the present invention.

FIGS. 4A and 4B are side views of the sheet feed roll according to an embodiment of the present invention.

FIG. 5 is a view showing the results of observation of the outer peripheral surface of a separating roll in Test Example 2.

FIG. 6 is a view showing the method of Test Example 3.

FIG. 7 is a view showing the method of Test Example 4.

FIG. 8 is a view showing the results of observation of end portions of a separating roll in Test Example 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail based on the embodiments offered below with reference to the accompanying drawings.

FIG. 1 is a schematic perspective view representing an image of a sheet feed roll according to the present invention. As shown in FIG. 1, a sheet feed roll 1 has an elastic layer 3, comprising polyurethane or the like, provided on a shaft 2. The sheet feed roll of the present invention has an irregular portion, whose section is in a corrugated form, formed on the outer peripheral surface of the elastic layer 3. A concavity constituting the irregular portion extends in the axial direction of the roll. That is, the concavity is formed from a slot extending along the axial direction of the roll. The term “axial direction” is taken to include a direction at an angle of 45 degrees or less with respect to the axis of the roll. A plurality of the concavities or the single concavity may be provide in the circumferential direction or the axial direction. An example of a case where a plurality of the concavities are provided on the outer peripheral surface of the roll is schematically expressed as an enlarged view of the outer peripheral surface in FIG. 2. The shaded parts in FIG. 2 represent the concavities. The sizes of the respective concavities and convexities may be the same (FIG. 3A) or different (FIG. 3B), as shown in FIGS. 3A, 3B which are enlarged sectional views taken in the circumferential direction of the roll. The irregular portion of the sheet feed roll according to the present invention is of a corrugated cross-section which is smooth without corners. This irregular portion does not have a grain pattern with steps as shown in FIG. 1(a) of Japanese Patent Application Laid-Open (kokai) No. 8-108591.

The widths of the concavities are preferably 500 μm or less. If the widths of the concavities are larger than 500 μm, the distance over which the sheet is fed becomes short, resulting in a tendency toward poor sheet feed performance. The width of the concavity refers to the spacing between intermediate sites located in a zone ranging from the tops of the adjacent convexities to the bottom of the concavity formed between the convexities, as shown in FIGS. 3A, 3B; namely, the width of the concavity refers to a width based on a central plane which is defined by the average of the heights of the irregularities shown in FIGS. 3A, 3B. The widths of the concavities, and the widths and heights of the convexities (to be described later) can be measured, for example, by an ordinary surface roughness measuring machine (Surfcorder SE3500: Kosaka Laboratory Ltd.).

The widths of the convexities are preferably 500 μm or less. In this case, the concavities constituting the irregular portion are constituted by a plurality of slots arranged with spacing. If the widths of the convexities are larger than 500 μm, influences from load, the speed of sheet feed, and the type of the sheet are easily exerted, or the distance of feed is short, leading to a tendency toward poor sheet feed performance. The width of the convexity refers to the spacing between intermediate sites located in a zone ranging from the bottoms of the adjacent concavities to the top of the convexity formed between the concavities, as shown in FIGS. 3A, 3B; namely, the width of the convexity refers to a width based on the central plane which is defined by the average of the heights of the irregularities shown in FIGS. 3A, 3B.

When the outer peripheral surface of the roll is partitioned by a lattice of cells 1 mm square each, it is preferred that one or more of the convexities and one or more of the concavities be present in each of the cells throughout the outer peripheral surface of the roll. However, the roll may be such that there are none of the concavities and convexities in a part of the roll, for example, at the end of the roll, or there are the concavities and convexities partly on the roll.

The heights of the convexities are preferably 50 to 150 μm. If paper dust or the like fills in the concavities, sheet feed performance worsens. If the heights of the convexities are set at 50 to 150 μm, it becomes possible to trap paper dust or the like in the relevant concavities. Upon repeated passage of sheets, therefore, sheet feed performance is not deteriorated, and sheet feed performance is stabilized. The height of the convexity refers to the dimension from the bottom of the concavity to the top of the convexity.

The concavity and the convexity each preferably have a length in the axial direction which is two times or more the length thereof in the circumferential direction. If the length in the axial direction of the concavity is smaller than two times the length in the circumferential direction of the concavity, the effect of trapping paper dust declines. If the length in the axial direction of the convexity is smaller than two times the length in the circumferential direction of the convexity, the area of contact between the sheet and the roll becomes too small, thus deteriorating sheet feed characteristics.

The sheet feed roll of the present invention preferably has a hardness of 25 to 50° according to JIS A. Its rebound resilience is preferably 50 to 80%. Deviations from these ranges would render the sheet feed roll susceptible to a load, a sheet feed speed, and the type of the sheet, or result in a short distance fed, thus tending to deteriorate sheet feed performance.

The ten-point mean roughness (surface roughness) Rz is preferably 40 to 120 μm, more preferably 50 to 80 μm. If the surface roughness is too low, the paper dust trapping effect is not obtained. Too high surface roughness results in unstable sheet feed characteristics. The ten-point mean roughness Rz is specified by JIS B0601-1994. The ten-point mean roughness Rz is the sum of the mean height of the five highest profile peaks and the mean depth of the five deepest profile valleys measured from the mean line over a sampling length of a roughness profile curve, the height and the depth being measured along the direction perpendicular to the mean line. Rz may be determined by means of a microscope for measurement of surface profile or a similar instrument.

The material for the elastic layer 3 is not limited, and the elastic layer 3 can be subjected to forming, for example, using EPDM, silicone, chloroprene, NBR, or polyurethane. However, it is preferred to use polyurethane, in particular. Since polyurethane is particularly excellent in wear resistance, the wear of the convexities in their height direction is suppressed, so that the paper dust trapping effect can be maintained for a long period of time.

The irregular surface of the sheet feed roll of the present invention can be formed, for example, by forming using a mold. The method of creating a grained surface, which constitutes the irregular surface, is not limited. However, a predetermined irregular surface can be formed conveniently and at a low cost by machining, such as sand blasting or shot blasting, and other chemical treatment methods, such as corrosion treatment.

An example of the method for forming the above-mentioned irregular surface in the mold comprises cutting a steel stock having a hardness of 38 (HRC) or higher to obtain a mold, masking the mold into a desired pattern, and then blasting the mold with a predetermined medium. In this case, a square-cornered medium (sand) which has a particle size of 50 to 300 μm and has variations of ±10% from the reference particle size, is preferably used in blasting. It is preferred to apply a hard chromium plating to the surface blasted in this manner.

Using the mold with the irregular surface formed in the above-described manner, the sheet feed roll of the present invention can be produced by the same method as the method of producing an ordinary roll.

Also preferably, outer peripheral corners in opposite end portions in the longitudinal direction of the sheet feed roll of the present invention have a C-surface or an R-surface; that is, the outer peripheral end portions are thin-layered. By so forming C-surfaces or R-surfaces in the outer peripheral end portions, excellent wear resistance is imparted to the sheet feed roll, and wear (chipping) at the end portions of the sheet feed roll can be prevented upon long-term use. The C-surface or R-surface is preferably formed such that a portion in a range of 1 to 2 mm from a reference position of the end surface and outer peripheral surface of the roll shape, namely, from the position of the roll end in the absence of the C-surface or R-surface, has been removed. That is, as shown in FIGS. 4A, 4B, a sheet feed roll 1A or 1B according to the present invention preferably has such a C-surface 5 or an R-surface 6 that lengths L₁ and L₂ from a standard position S are 1 to 2 mm. The C-surface represents a chamfer surface defined by JIS Z8317 (dimensions in drawing), while the R-surface represents an arcuate surface defined by JIS Z8317 (dimensions in drawing). However, the C-surface and R-surface include similar chamfer surfaces and curved surfaces resembling an arcuate surface.

The above-described C-surface or R-surface is preferably formed simultaneously with the molding of the roll.

EXAMPLES Example 1

A polyol (100 parts by weight) produced by dehydration condensation of 1,9-nonanediol, 2-methyloctanediol, and adipic acid was mixed with 30 parts by weight of 4,4′-diphenylmethane diisocyanate (MDI), 6 parts by weight of diethylene glycol (DEG) as a chain extender, and 22 parts by weight of P3403 (DAICEL CHEMICAL INDUSTRIES, LTD.) being an ether-ester-based triol having a molecular weight of 4,000 as a crosslinking agent. The mixture was charged into a mold preheated at 150° C. and having an entire surface grained. The configuration of the grained surface of the mold is described in Table 1. A curing product of the charge was aged with heating for 12 hour sat 100° C., was subjected to a cutting-off operation, and force-fitted with a shaft having an external diameter of 15 mm to obtain a separating roll comprising polyurethane and having an outer diameter of 25 mm, an inner diameter of 15 mm, and a width of 25 mm.

Example 2

A separating roll was obtained in the same manner as in Example 1, except that the grained surface was as shown in Table 1.

Example 3

A separating roll was obtained in the same manner as in Example 1, except that the grained surface was as shown in Table 1, the amount of DEG was 2 parts by weight, and the amount of P3403 was 125 parts by weight.

Example 4

The separating roll of Example 1 was chamfered at the opposite end portions such that the lengths L₁ and L₂ from the reference position S were 1 mm (to be hereinafter referred to as “C=1”) The so chamfered separating roll was used as the separating roll of Example 4.

Comparative Examples 1 to 3

Separating rolls were obtained in the same manner as in Example 1, except that the grained surfaces were as shown in Table 1.

Comparative Examples 4 and 5

Separating rolls were obtained in the same manner as in Example 1, except that the grained surfaces were as shown in Table 1, and EPDM was used instead of the polyurethane.

Comparative Example 6

A separating roll was obtained in the same manner as in Example 1, except that the crosslinking agent was 1 part by weight of trimethylolpropane (TMP).

Comparative Example 7

A separating roll was obtained in the same manner as in Example 1, except that the roll was prepared using a mold without a grained surface, and was polished with a grinding wheel to render the surface shape of the roll polishing marks.

Test Example 1

The separating rolls of the Examples and the Comparative Examples were measured for the hardness (JIS A), rebound resilience at 25° C. (JIS K6251), Rz (JIS B0601:1994), the width of the concavities, the width of the convexities, and the height of the convexities. The results are described in Table 1, along with the direction of the concavities and the shape of the opposite end portions. The rolls which were not chamfered are indicated by C=0 in Table 1. The results show that the irregular surface having the same width of the concavities, the same width of the convexities, and the same height of the convexities as those of the mold was formed in each separating roll. TABLE 1 Rebound Height of Ratio of width in Shape of resil- Width of Width of con- circumferential direction opposite Hardness ience concavities convexities vexities Direction of to width in axial direction end Rz Material JIS A° % μm μm μm concavities Convexities Concavities portions μm Ex. 1 Polyurethane 45 70 400 or less 400 or less 80 Axial 1/3 1/3 C = 0 65 Ex. 2 Polyurethane 45 70 400 or less 400 or less 130 Axial 1/5 1/5 C = 0 105 Ex. 3 Polyurethane 33 60 400 or less 400 or less 80 Axial 1/7 1/5 C = 0 65 Ex. 4 Polyurethane 45 70 400 or less 400 or less 80 Axial 1/3 1/3 C = 1 65 Comp. Polyurethane 45 70 700-1000 400 or less 80 Axial 1/3 1/3 C = 0 65 Ex. 1 Comp. Polyurethane 45 70 400 or less 800-1200 80 Axial 1/2 1/2 C = 0 65 Ex. 2 Comp. Polyurethane 45 70 400 or less 400 or less 80 Random* 1/1 1/1 C = 0 65 Ex. 3 Comp. EPDM 35 80 400 or less 400 or less 80 Axial 1/3 1/3 C = 0 65 Ex. 4 Comp. EPDM 43 70 400 or less 400 or less 80 Axial 1/3 1/3 C = 0 65 Ex. 5 Comp. Polyurethane 68 70 400 or less 400 or less 80 Axial 1/3 1/3 C = 0 65 Ex. 6 Comp. Polyurethane 45 70 — — 35 Polishing — — C = 0 18 Ex. 7 marks *“Random” means to include the concavities extending along the direction perpendicular to the axial direction (namely, the circumferential direction).

Test Example 2

The outer peripheral surface of the roll in Example 1 was observed. The results are shown in FIG. 5. The cells of the lattice, each measuring 1 mm square, are indicated by white lines. As shown in FIG. 5, concavities and convexities were formed in the axial direction on the outer peripheral surface of the roll.

Test Example 3

As shown in FIG. 6, a free roll 12 provided rotatably was pressed under a load against a separating roll 11 of each of the Examples and the Comparative Examples, with a sheet 13 being interposed between the free roll 12 and the separating roll 11. When the separating roll 11 was rotationally driven, the amount of movement of the sheet per rotation of the separating roll was measured by a laser feed monitor (FC2010, KEYENCE CORP.) to investigate the efficiency of sheet feed and the stability of sheet feed. The measuring conditions were changed as shown by Nos. 1 to 8 in Table 2. The measuring environment was 2.3° C.×50% RH. TABLE 2 Measuring Load Sheet feed speed condition No. gf mm/s Type of sheet No. 1 100 125 Type 6200* No. 2 Hammer mill* No. 3 500 Type 6200 No. 4 Hammer mill No. 5 400 125 Type 6200 No. 6 Hammer mill No. 7 500 Type 6200 No. 8 Hammer mill *Type 6200: 64 g/m², RICOH CO., LTD. *Hammer mill: 108 g/m², INTERNATIONAL PAPER

TABLE 3 Amount of sheet movement per rotation of sample under each test condition Chipping (mm) Average Efficiency of end No. 1 No. 2 No. 3 No. 4 No. 5 No. 6 No. 7 No. 8 σ mm % portions Ex. 1 72.74 76.62 71.14 75.15 70.86 75.92 69.66 75.02 2.63 73.39 93.5 Yes Ex. 2 71.55 75.43 71.11 75.04 70.67 73.85 68.81 74.03 2.36 72.56 92.4 Yes Ex. 3 71.96 74.16 71.53 74.39 71.23 73.35 69.20 73.26 1.74 72.38 92.2 Yes Ex. 4 72.58 72.51 71.22 75.20 70.82 75.18 69.53 74.89 2.17 72.74 92.7 No Comp. 70.31 73.44 68.02 70.97 68.43 70.93 63.87 70.33 2.83 69.54 88.6 Yes Ex. 1 Comp. 70.94 72.31 67.72 71.41 67.28 71.13 62.33 69.77 3.27 69.11 88.0 Yes Ex. 2 Comp. 71.05 74.34 68.98 72.63 65.63 72.19 65.16 71.51 3.35 70.21 89.4 Yes Ex. 3 Comp. 71.40 74.54 68.84 72.98 67.90 73.10 65.87 72.63 3.03 70.91 90.3 Yes Ex. 4 Comp. 68.26 74.38 67.48 74.31 63.30 73.13 61.22 73.29 5.17 69.42 88.4 Yes Ex. 5 Comp. 66.72 71.38 66.31 72.11 62.16 69.31 60.10 68.33 4.21 67.05 85.4 Yes Ex. 6 Comp. 69.00 74.87 68.08 72.38 67.40 72.41 65.19 71.28 3.19 70.08 89.3 Yes Ex. 7 *Efficiency = (Actually measured amount of sheet movement/Circumferential length of sample) × 100

In Examples 1 to 4, in which the samples comprised polyurethane having a hardness of 25 to 50° (JIS A) and rebound resilience of 50 to 80%, the direction of the concavities was the axial direction of the roll, the width of the convexities was 500 μm or less, the width of the concavities was 500 μm or less, and the height of the convexities was 50 to 150 μm, it was found that the efficiency of sheet feed was particularly high, and the sheet feed performance was satisfactory. It was also found that the samples of Examples 1 to 4 had small standard deviations σ, were not susceptible to load, the sheet feed speed, and the type of the sheet, and were stable in sheet feed performance.

In Comparative Example 3, in which the direction of the concavities was random, on the other hand, the sheet feed efficiency was not so good as in Examples 1 to 4, and the sheet feed performance was not stable. In Comparative Example 1, in which the width of the concavities was not 500 μm or less, moreover, such satisfactory characteristics as in Example 1 were not obtained, even when the other conditions were set to be the same as those in Example 1 affording satisfactory performance. The same can be said of Comparative Example 2 in which the width of the convexities was not 500 μm or less, and Comparative Example 6 in which the hardness was outside the range of 25 to 50°.

Test Example 4

As shown in FIG. 7, a free roll 22 provided rotatably was pressed under a load of 200 gf against the separating roll 11 of each of the Examples and the Comparative Examples fixed so as not to rotate, with a sheet 23 (color laser OHP sheet TR-3, CANON INC.) being interposed between the free roll 22 and the separating roll 11. The sheet 23 was pulled out by 120 mm at a rate of 50 mm/sec with the use of a load cell 24 attached to one end of the sheet 23. Then, the state of end portions of the separating roll 11 was observed. The results are shown in Table 3. End portions of the separating roll of Example 1 were microscopically observed, and the results are shown in FIG. 8.

As shown in Table 3, Example 4, in which the opposite end portions of the separating roll were chamfered to have C-surfaces, showed no chipping in the opposite end portions of the roll, demonstrating excellent wear resistance. The separating rolls other than that of Example 4, on the other hand, underwent chipping in the opposite end portions, as shown in FIG. 8.

Although the preferred embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions and alterations can be made therein-without departing from the spirit and scope of the invention as defined by the appended claims. 

1. A sheet feed roll having a concavity and a convexity formed on an outer peripheral surface thereof, an irregular portion composed of said concavity and said convexity being of a corrugated cross-sectional shape, and said concavity extending along an axial direction of said roll.
 2. The sheet feed roll according to claim 1, wherein a width of said concavity is 500 μm or less.
 3. The sheet feed roll according to claim 1, wherein a width of said convexity is 500 μm or less.
 4. The sheet feed roll according to claim 1, wherein a width of said concavity is 500 μm or less, and a width of said convexity is 500 μm or less.
 5. The sheet feed roll according to claim 1, wherein when the outer peripheral surface of said roll is partitioned by a lattice of cells 1 mm square each, one or more of said convexities and one or more of said concavities are present in each of said cells.
 6. The sheet feed roll according to claim 1, wherein a height of said convexity is 50 to 150 μm.
 7. The sheet feed roll according to claim 1, comprising polyurethane having a hardness of 25 to 50° (JIS A), and rebound resilience of 50 to 80%.
 8. The sheet feed roll according to claim 1, having Rz of 40 to 120 μm.
 9. The sheet feed roll according to claim 1, wherein a length in the axial direction of said concavity is two times or more a length in a circumferential direction of said concavity.
 10. The sheet feed roll according to claim 1, wherein a length in the axial direction of said convexity is two times or more a length in a circumferential direction of said convexity.
 11. The sheet feed roll according to claim 1, wherein outer peripheral corners in opposite end portions in a longitudinal direction of said sheet feed roll have C-surfaces or R-surfaces.
 12. A sheet feed roll comprising polyurethane having a hardness of 25 to 50° (JIS A), and rebound resilience of 50 to 80%, and said sheet feed roll having a concavity and a convexity formed on an outer peripheral surface thereof, an irregular portion composed of said concavity and said convexity being of a corrugated cross-sectional shape, and wherein said concavity extends along an axial direction of said roll, a width of said concavity is 500 μm or less, a width of said convexity is 500 μm or less, a height of said convexity is 50 to 150 μm, and Rz of said sheet feed roll is 40 to 120 μm. 